jQuery JSON parse - "Object not defined"

Question

Currently working for the first time with JSON and with little experience of jQuery. I have this function that gets triggered on "success" of $.ajax request:

function(data) {

    $.each(data.notifications, function(notifications) {
        alert('New Notification!');
    });

}

However I get an error in the firebug console stating "object is undefined" "length = object.length".

The JSON response is:

["notifications",[["test would like to connect with you",{"Accept":"\/events\/index.php\/user\/connection?userId=20625101&action=accept","Decline":"\/events\/index.php\/user\/connection?userId=20625101&action=decline"}]]]

I guess it has something to do with the number of []s but the JSON was encoded by PHP using json_encode()

Any help would be appreciated!

Thanks :)

Vivin Paliath · Accepted Answer · 2012-07-02 18:17:23Z

What you have is a JSON Array. I'm guessing you were looking for something like this:

{
    "notifications": [
        ["test would like to connect with you",
        {
            "Accept": "\/events\/index.php\/user\/connection?userId=20625101&action=accept",
            "Decline": "\/events\/index.php\/user\/connection?userId=20625101&action=decline"
        }]
    ]
}

Although I think a better structure would be:

{
    "notifications": [
        {
            "message": "test would like to connect with you",
            "Accept": "\/events\/index.php\/user\/connection?userId=20625101&action=accept",
            "Decline": "\/events\/index.php\/user\/connection?userId=20625101&action=decline"
        }
    ]
}

This way notification becomes a property of the object, which means you can access it via data.notifications. Otherwise you'd have to access the notifications via data[1] (data[0] would contain the string "notifications" which essentially becomes meaningless).

The following example should give you an idea as far as setting up your data in PHP:

<?php
  $array = array(
      "notifications" => array(
          array(
              "message" => "Test would like to connect with you",
              "Accept" => "/events/index.php/user/connection?userId=20625101&action=accept",
              "Decline" => "/events/index.php/user/connection?userId=20625101&action=decline"
          )
      )
  );

  echo json_encode($array);
?>

UltraInstinct · Accepted Answer · 2012-07-02 18:16:29Z

2

Your PHP response should actually be:

{
    "notifications": [
       ["test would like to connect with you",
        {
           "Accept":"\/events\/index.php\/user\/connection?userId=20625101&action=accept",
           "Decline":"\/events\/index.php\/user\/connection?userId=20625101&action=decline"
        }
       ]
    ]
}

Note that with the above, notification is a field inside the object that the string represents. That will allow you to iterate, the way you are doing it with $.each(..).

The way you are doing is it by having an array (note the initial [ and the last ] in the response). The error is because $.each invokes data.notification.length where .length is an operation on undefined.

PHP side code should be somewhat like below:

echo json_encode(array("notifications" => $notifications));

instead of (my guess):

echo json_encode(array("notification", $notifications));

edited Jul 2, 2012 at 18:16

answered Jul 2, 2012 at 18:08

UltraInstinct

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2 Comments

cud_programmer Over a year ago

Thank you! Do you know why my json_encode($array) is returning a JSON array rather than object?

cud_programmer Over a year ago

thanks for your help! I've figured out why it was giving JSON array - because I wasn't supplying name=>value pairs in array. Used to C and Java arrays :)

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